Developments in WIS Development

This paper presents findings from a longitudinal field study of web-design undertaken in a webdevelopment company. The main contribution is a comparison of some early predictions on the implications of the increased usage of www-technologies for more complex information systems and core findings from two field studies of a specific web-development work setting. The two studies are snapshots from a longitudinal study. Focus in the studies has been on organization of the development work, essential characteristics of the development work, and core characteristics of the products developed. Many of the core problems to be handled in web-based information systems (WIS) development are quite analogous to challenges known from traditional information systems development, although the pace and the number of involved competencies increase, there is a lack of standards in many areas, and there is an increase in communication problems between the different competence groups

Evaluation of Item Response Theory Models for Nonignorable Omissions

When competence tests are administered, subjects frequently omit items. These missing responses pose a threat to correctly estimating the proficiency level. Newer model-based approaches aim to take nonignorable missing data processes into account by incorporating a latent missing propensity into the measurement model. Two assumptions are typically made when using these models: (1) The missing propensity is unidimensional and (2) the missing propensity and the ability are bivariate normally distributed. These assumptions may, however, be violated in real data sets and could, thus, pose a threat to the validity of this approach. The present study focuses on modeling competencies in various domains, using data from a school sample (N = 15,396) and an adult sample (N = 7,256) from the National Educational Panel Study. Our interest was to investigate whether violations of unidimensionality and the normal distribution assumption severely affect the performance of the model-based approach in terms of differences in ability estimates. We propose a model with a competence dimension, a unidimensional missing propensity and a distributional assumption more flexible than a multivariate normal. Using this model for ability estimation results in different ability estimates compared with a model ignoring missing responses. Implications for ability estimation in large-scale assessments are discussed

Developing Instructional Quality in School-Networks. Baseline Conditions for the Implementation in a Pilot Program to Increase the Efficiency of Mathematics and Science Instruction

Implementationsforschung wird unter dem Aspekt bedeutsamer Ausgangsbedingungen an den von einer Innovation betroffenen Institutionen betrachtet. Im Blickpunkt steht der Qualitätsentwicklungsansatz des Programms zur "Steigerung der Effizienz des mathematisch-naturwissenschaftlichen Unterrichts" (SINUS) der Bund-Länder-Kommission für Bildungsplanung und Forschungsförderung. Dabei wird geprüft, ob die beteiligten Programmschulen eine besondere Selektion in Bezug auf schulbezogene Ausgangslagen darstellen. Es werden vier Bereiche betrachtet: Familiärer Hintergrund der Schülerinnen und Schüler, motivationale Orientierungen und Präferenzen im mathematisch-naturwissenschaftlichen Bereich, Schulklima und Kompetenzen in Mathematik und Naturwissenschaften. Bei der Erhebung der Ausgangslage wurden 136 SINUS-Schulen mit national entwickelten PISA-Instrumenten getestet. Die Ergebnisse können daher mit Daten einer für Deutschland repräsentativen Stichprobe (PISA/E 2000) verglichen werden. Die Ergebnisse zeigen, dass sich das Programm nicht systematisch auf eine Selektion besonderer Schulen bezieht. Sie werden zum einen in Hinblick auf die Implementationsforschung, zum anderen in ihrer Bedeutung für die allgemeine Übertragbarkeit der Implementation an weiteren Schulen diskutiert. (ZPID)In the article implementation research is treated in the light of relevant conditions at schools affecting an innovation. The quality development approach of the pilot program to increase the efficiency of mathematics and science instmction (SINUS) serves as an example to investigate this question. From an implementation research perspective it is important to examine which conditions foster or hamper the implementation of the approach. To study these questions systematic data concerning relevant conditions at the beginning of the program have to be available. Baseline data from the participating schools will be reported. Whether or not the participating schools have been recruited from a special selection of (e. g. excellent) schools will also be reported. Four aspects will be looked at: family background of the students, motivational variables with regard to mathematics and science teaching, school climate and competencies in mathematics and science. 136 program schools took part in the baseline study using nationally developed German PISA instruments. The results can, therefore, be compared with a representative group of schools (PISA/E 2000, the national representative extension of the German PISA sample). The study provides information on relevant baseline conditions in the participating schools that is needed as a prerequisite for carrying out implementation research. Results show that the program does not draw on a special selection of schools. These results are discussed in the light of implementation research, and in their meaning for generalizing the implementation for a larger group of schools. (DIPF/Orig.

Composition of natural phytoplankton community has minor effects on autochthonous dissolved organic matter characteristics

Dissolved organic matter (DOM) is an important component of nutrient cycling, but the role of different organisms controlling the processing of autochthonous DOM remains poorly understood. Aiming to characterize phytoplankton-derived DOM and the effects of complex pelagic communities on its dynamics, we incubated natural plankton communities from a temperate mesohaline estuary under controlled conditions for 18 days. The incubations were carried out in contrasting seasons (spring and autumn) and changes in the planktonic community (phytoplankton, bacteria and microzooplankton), nutrients and DOM were assessed. Our results highlight the complexity of DOM production and fate in natural planktonic communities. Small changes in DOM composition were observed in the experiments relative to the orders-of-magnitude variations experienced in the phytoplankton assembly. We argue that the tight coupling between microbial processing and DOM production by phytoplankton and grazers stabilizes variations in quantity and characteristics of autochthonous DOM, resulting in apparently homogeneous semi-labile DOM pool throughout the experiments. However, seasonal differences in the production and processing of DOM were observed, reflecting differences in the nutrient regimes and initial DOM characteristics in each experiment, but also likely influenced by changes in the successional status of the pelagic community. Acknowledging that characteristics of the DOM derived from phytoplankton growth can vary broadly, heterotrophic processing and successional status of the community are synergistically important factors for shaping those characteristics, and thus affecting the seasonal signature of the semi-labile autochthonous DOM pool.peerReviewe

What is marine biodiversity? Towards common concepts and their implications for assessing biodiversity status

Biodiversity' is one of the most common keywords used in environmental sciences, spanning from research to management, nature conservation, and consultancy. Despite this, our understanding of the underlying concepts varies greatly, between and within disciplines as well as among the scientists themselves. Biodiversity can refer to descriptions or assessments of the status and condition of all or selected groups of organisms, from the genetic variability, to the species, populations, communities, and ecosystems. However, a concept of biodiversity also must encompass understanding the interactions and functions on all levels from individuals up to the whole ecosystem, including changes related to natural and anthropogenic environmental pressures. While biodiversity as such is an abstract and relative concept rooted in the spatial domain, it is central to most international, European, and national governance initiatives aimed at protecting the marine environment. These rely on status assessments of biodiversity which typically require numerical targets and specific reference values, to allow comparison in space and/or time, often in association with some external structuring factors such as physical and biogeochemical conditions. Given that our ability to apply and interpret such assessments requires a solid conceptual understanding of marine biodiversity, here we define this and show how the abstract concept can and needs to be interpreted and subsequently applied in biodiversity assessments